Giger's Involvement With Prometheus

Space Screamer
MemberOvomorphJuly 10, 20121235 Views3 RepliesI was reading The Art Book for the film and Arthur Max points out several times that they used Giger's original work on Alien as a starting point for Prometheus, but they opted to tone down the organic qualities of his designs.
Does anyone know why Giger was not directly involved in this film, other than the mural he created? Was he approached to be a part of the production and declined, or did Scott just decide not to use him?